Spotting Detail Differences on Your Favorite Railroads' Paint Schemes

It is always good to look at your favorite railroads' paint schemes through the years and see any detail differences they might have.  This helps you see details on locomotives and spot what era a locomotive is from. 
Grand Trunk Western, for example, switched from black to blue.  The red ends stayed the same, so especially in a black and white photo, at times, it can be hard to spot if certain locomotives are painted in black or blue.
Right before committing to painting, it is always a good idea to check as many references as possible to see if a locomotive is painted a certain way.  As in the drawings above many Grand Trunk Western locomotives were painted in black, blue, and also green.
Your eye will catch details, such as the longer arm on the "G" on the black paint scheme as compared to the blue paint scheme.  Many times, details on locomotives, such as horn and antenna placements give clues to the era or shop a locomotive is from.  This can give clues to variances in paint schemes, especially when looking at black and white photos.
Spotting details on locomotives is key to the challenge of lettering placement.  Notice the placement of the "GT" logo is towards the front and center of most of the locomotives, however, it is towards the rear of the GP9.  This is because the GP9 has grills located in the center of the hood, making center placement a challenge.
The more you spot on locomotives, the better your drawings will become.  With each detail you see, the more fun you will have.  Enjoy drawing trains.